The present inventors have disclosed a method for producing blue coloring composite obtained, firstly, by the application of a microorganism to the extract of gardenia fruits (Gardenia jasminoides var. grandiflora) (Japanese Patent Application Publication No. 13971/1977), and secondly by the application of a primary amino group-containing substance to the aglycones of iridoid glycosides (Japanese Patent Application No. 130131/1975), and have elucidated the mechanism for the formation of these coloring compounds and their structures (Japanese Patent Application No. 49418/1977). Further studies revealed that the red coloring composite, with maximum absorption at 520-540 nm, is formed between iridoid compounds where, if necessary, by application of microorganism or enzyme, or chemical method, either alone or in combination, in the case of glycosides to obtain the aglycone, and substances containing a primary amino group. Physico-chemical properites of these coloring composite were investigated and the present invention was completed.